Endosseous root form implants are devices that are mainly used for support of dental prosthetic pieces. They can be also used for the anchorage of orthodontic devices.
Prior art dental implant treatments suffer from the following limitations: (1) Duration of Treatment—the treatment has a long healing period, after implant placement and before teeth restoration of: 3-4 months in the lower jaw, 4-6 months in the upper jaw, and 6-9 months for bone graft cases such as ridge augmentation and sinus lift; (2) The implantation failure rate is higher with respect to those suffering from osteoporosis, or reduced bone mass and density, due to a low degree of osseointegration. An implant is generally considered to be osseointegrated when it contacts the adjacent bone without any progressive relative movement therebetween. It is estimated that 20% of potential implantees for dental implantation suffer from this problem, this value constantly increasing due to the wordlwide population increase of elderly people; (3) An implantation cannot be performed when there is not enough available bone at the implantation site. It is estimated that 30% of potential implantees for dental implantation suffer from this problem. These patients have to undergo bone graft procedures such as ridge augmentation and sinus lift.
It would therefore be desirable to provide an implant device for stimulating osteogenesis, or bone development, and to thereby increase the implantation success rate as well as to shorten the treatment duration during which the bone-forming cells and the bone tissue surrounding the implant sufficiently develop and become osseointegrated.
The use of electric and electromagnetic fields to stimulate biologic systems has received attention in medicine. In the field of orthopedics, a pulsed electromagnetic field (PEMF) has been successfully used to induce healing in fractures of human long bones that proved resistant to conventional treatment and frequently required amputation. [Ryaby, J. T. (1998), “Clinical Effects of Electromagnetic and Electric Fields on Fracture Healing”, Clinical Orthopedics and Related Research 355: 205-215] Applied electrical and electromagnetic fields can alter the normal electrical states of bone and cartilage, induce increased rates of cellular division and metabolism, and thus promote increased healing of bony and cartilage defects.
Muscle, ligament, bone, cartilage, blood, and adult stem-cell production all respond to electric and electromagnetic fields, and these biophysical field agents can be applied in therapeutic contexts. Electric and electromagnetic fields regulate extra-cellular matrix synthesis and stimulate repair of fractures and nonunions. Studies of electric and electromagnetic fields suggest they (1) regulate proteoglycan and collagen synthesis and increase bone formation in models of endochondral ossification, (2) accelerate bone formation and repair, (3) increase union rates in fractures previously refractory to healing, and (4) produce results equivalent to bone grafts. Electric and electromagnetic fields regulate the expression of genes in connective tissue cells for extra-cellular matrix proteins, which results in an increase in cartilage and bone. They also increase gene expression for and synthesis of growth factors, which may be an intermediary mechanism of activity and may amplify field effects through autocrine and paracrine signaling.
However, electromagnetic fields have not been used heretofore to stimulate osteogenesis and osseointegration with respect to dental implants. Dental implants are anchored into the jaw bone, and the entire circumference of an implant has to be osseintegrated with the jaw bone, requiring a long treatment duration as described hereinabove. An electromagnetic treatment to effectively stimulate osseointegration in dental implants therefore has to be ongoing, and an ambulatory treatment whereby a dental implantee is irradiated at a clinic by an electromagnetic field during a limited number of sessions per week will not be efficacious.
An electromagnetic treatment is energy intensive, and an electromagnetic field generator carried by the implantee and in constant use needs to be constantly recharged. Due to the need of constant recharging, an electromagnetic field generator cannot be conveniently localized within the oral cavity.
U.S. Pat. No. 5,292,252 to Nickerson et al discloses a stimulator healing cap for enhancing in a patient the growth of bone cells and bone tissue surrounding a dental implant. The stimulator healing cap includes a top cap portion containing a direct current source, and a threaded portion which attaches to the implant in the same way as a cover screw. In one embodiment, the current source is coupled to a coil which surrounds a longitudinal core creating an electromagnetic field around the implant and thus in the surrounding bone tissue.
The electromagnetic field that is generated by the current source is a static magnetic field (SMF), and the stimulation of bone growth by a SMF has not yet been definitively established. Another disadvantage of this healing cap is that the constantly operating battery that can be housed within its small internal volume is of an insufficient capacity for the required healing period.
U.S. Pat. No. 6,034,295 to Rehberg et al discloses an implantable device, including a dental implant, formed with an internal cavity into which the bone tissue that surrounds the implanted device is intended to grow. The device is provided with at least two electrodes, one of which is located within the cavity and spaced apart from the inside of the body that forms the cavity, and a second electrode when the body is made of an electrically conductive material, which together with the internal electrode, forms a kind of coaxial structure for generating a low-frequency alternating current for promoting tissue growth. However, an electric field generated by electrodes will not propagate beyond the outermost electrode, and is therefore incapable of stimulating osteogenesis in damaged or osteoporotic tissue outwardly spaced from the implant.
It is an object of the present invention to provide a dental implant device for stimulating osteogenesis.
It is an additional object of the present invention to provide a dental implant device for stimulating osseointegration.
It is an additional object of the present invention to provide a dental implant device for effectively stimulating osteogenesis by means of a pulsed electromagnetic field.
It is an additional object of the present invention to provide a dental implant device for stimulating osteogenesis which does not require a battery for powering the device to be replaced or recharged.
Other objects and advantages of the invention will become apparent as the description proceeds.